Electronic tags, such as Electronic Article Surveillance (EAS) tags or radio frequency identification (RFID) tags, have been widely used in retail checkout or inventory control to prevent shoplifting and/or unauthorized removal of articles from retail stores. Typically, these tags are attached to articles to store information describing the attached articles to help in tracking the movement of the articles and in updating the inventory records. It is desirable to combine the inventory use with EAS, to avoid the requirement for an inventory RFID tag and a separate EAS device.
One surveillance scheme is based on the information stored inside a tag to identify an attached article at an exit gate. For example, a database can be maintained to represent an up-to-date inventory of the store and queried to tell whether the article has been sold. However, a very high speed database may be required for this scheme to be effective such that counter actions can be initiated within fractions of seconds before it is too late to guard against the removal of unsold articles. The database must also be kept real time to within a few seconds from possibly many point of sale terminals
Alternatively, a status bit may be stored in a tag to indicate whether an article has been sold or not and updated accordingly at a checkout registry. However, the status bit can not distinguish a tag in the store's inventory from a foreign tag brought into the store, which has possibly not been properly disabled at the other store, thus triggering “false positive” alarms which cause difficulties in acting on the information.
Another method for EAS protection involves “killing” or deactivating information in the tag permanently at the point of sale. If irreversible changes are to be made to the tags, then there is a possibility that an attacker might maliciously destroy the usefulness of the tags. Furthermore, password protection may then be required to update the status bit, or to kill the tag, or to permanently mark the tag as sold. As a result, databases may still be required to provide an inventory database and a password database for a surveillance scheme based on the status bit or other permanent changes to the tag. Such databases providing passwords may undesirable because of the requirement to maintain the information from different suppliers of tagged items, and the difficulties associated with interacting with the tag at the point of sale, obtaining the password and using to access permissions at the tag, and then changing the tag's memory appropriately, all during the momentary illumination of the tag by the beam of the reader at the point of sale.
Therefore, existing electronic surveillance systems do not provide a practical solution without requiring fast speed databases and/or password authentications.